The two wire electric arc spray process is the least expensive of the metal spraying processes used for applying metallic coatings. Any electrically conductive materials supplied in wire form can be sprayed. A wire feeder pushes two electrically charged wires through flexible conduits into an arc spray gun where the wires converge and an arc is created. The wires melt in the high temperature zone created by the arc and a concentrically located compressed air stream sustains the arc, atomizes the molten metallic material and conveys the metallic particles onto the object being coated. The particles cool and coalesce into a high quality metal coating on the object being coated.
The design of most electric arc spray guns is such that numerous problems arise in the operation of same. For example, the spray tips must be held in very close alignment and such alignment typically requires very accurate machining of the gun head which is a very expensive process. Alternatively, alignment of the spray tips and wires is sometimes achieved by the combination of a nozzle positioner, a nozzle cap and an arc shield retaining nut assembly. The nozzle positioner and the nozzle cap are supplied in different styles and types. All of these components must be removed each time the spray tips become worn necessitating their replacement. This cumbersome process results in the breakage of components and the possible misalignment of the spray tips. In addition to the problem of maintaining the spray tips in alignment, the design of most electric arc spray guns is such that the wires come together outside the orifice of the air cap. This design results in a less defined spray column which, in turn, reduces the density of the metallic coating on the object being coated. A well defined spray column is difficult to achieve and/or maintain when the wires come together outside the orifice of the air cap.
In view of the foregoing, it has become desirable to develop an electric arc spray gun wherein the spray tips can be held in precise alignment without expensive machining operations and wherein the gun produces a very well defined spray column in order to produce uniform metallic coatings having a high density.